Relation of serum ascorbic acid to mortality among US adults

Purpose: To examine the relation between serum ascorbic acid (SAA), a marke r of dietary intake (including supplements), and cause-specific mortality. Subjects and Methods: We analyzed data from a probability sample of 8,453 A mericans age greater than or equal to 30 years at baseline enrolled in the Second National Health and Nutrition Examination Survey (NHANES II), who we re followed for mortality endpoints. We calculated relative hazard ratios a s measures of disease association comparing the mortality rates in three bi ologically relevant SAA categories. Results: participants with normal to high SAA levels had a marginally signi ficant 21% to 25% decreased risk of fatal cardiovascular disease (CVD) (p f or trend = 0.09) and a 25% to 29% decreased risk of all-cause mortality (p for trend < 0.001) compared to participants with low levels. Because we det ermined that gender modified the association between SAA levels and cancer death, we analyzed these associations stratified by gender. Among men, norm al to high SAA levels were associated with an approximately 30% decreased r isk of cancer deaths, whereas such SAA levels were associated with an appro ximately two-fold increased risk of cancer deaths among women. This associa tion among women persisted even after adjustment for baseline prevalent can cer and exclusion for early cancer death or exclusion for prevalent cancer. Conclusions: Low SAA levels were marginally associated with an increased ri sk of fatal CVD and significantly associated with an increased risk for all -cause mortality. Low SAA levels were also a risk factor for cancer death i n men, bur unexpectedly were associated with a decreased risk of cancer dea th in women. If the association between low SAA levels and all-cause mortal ity is causal, increasing the consumption of ascorbic acid, and thereby SAA levels, could decrease the risk of death among Americans with low ascorbic acid intakes.